Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy
Round 1
Reviewer 1 Report
The authors investigated the corrosion behavior of three coatings (plasma electrolytic oxidation, plasma spray ceramic and hard anodizing) on 6082 aluminum alloy. The microstructure of the coatings was also investigated. The manuscript is within the scope of Processes Journal. However, before publication some concerns must be addressed:
Please detail the innovation of this study considering all the information already published? What are the main advances?
Introduction - Must be improved since it does not reflect the actual state of the art.
Materials and Methods - How many samples were studied in each electrochemical technique?
The results and discussion section must be organized. As presented ins very confusing. I suggest the authors present all the electrochemical results, followed by the optical observation and then the macro/micro structure analysis.
The Nyquist plots as presented are inaccurate since they must have square axis. Why the authors did not fit the EIS data? An equivalent electrical circuit must be introduced.
Table 3 - Please introduce the errors
Author Response
Dear Prof. Editors/ Reviewers
I thank you very much for your concern about my paper (Ref. No.: processes-386214) titled “Corrosion behavior of 6082 Aluminum Alloy Surface after Coating with Different Ceramic Coating processes" and appreciate your valuable comments on my work. Kindly, please find my replying on your comments in the following points:
For Editor: the paper title was modified to “Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy”
Reviewer #1:
Comments 1
Please detail the innovation of this study considering all the information already published? What are the main advances?
Authors Reply:
We studied the corrosion behavior of different three coatings on 6082-T6 aluminum alloy; Electrolytic Oxidation (PEO), Plasma Spray Ceramic (PSC) and Hard Anodizing (HA). There is hardly any comparison of these techniques using similar testing conditions. This work provides fundamental information about each technique as well as the comparison using same testing parameters. We believe this will provide better understanding for the readers to comprehend the advantages of each technique over other regarding corrosion.
Comment 2
Introduction - Must be improved since it does not reflect the actual state of the art.
Authors Reply:
The introduction part was modified on the suggestion of the reviewer and it has updated with recent studies and relevant literature.
Comment 3
Materials and Methods - How many samples were studied in each electrochemical technique?
Authors Reply:
A series of electrochemistry experiments were used to evaluate the corrosion performance of three types of ceramic coatings deposited on Al 6082-T6 alloy to study their enhancements on the substrate. These coatings are Plasma Electrolytic Oxidation (PEO) hard anodized (HA) and Plasma Spray Ceramic (PSC).
Each type of sample has been tested three times and the average value has been plotted.
Comment 4
The results and discussion section must be organized. As presented ins very confusing. I suggest the authors present all the electrochemical results, followed by the optical observation and then the macro/micro structure analysis.
Authors Reply:
There are multiple ways we can represent the results and discussion. The authors decided to follow the actual chronological order of the experimental procedure, which in our opinion, easier for the readers to follow. The sequence is in such a manner; 1) base metal characterization, 2) coating with three different techniques, 3) cross-sectional microstructure analysis of the coated samples, 4) Electrochemical testing, and finally 5) Micro-surface analysis of the corroded surfaces. These characterizations required either optical, SEM, chemical or any analysis followed in the sequence mentioned above.
Comment 5
The Nyquist plots as presented are inaccurate since they must have square axis. Why the authors did not fit the EIS data? An equivalent electrical circuit must be introduced.
Authors Reply:
AC impedance is an electrochemical measurement tool that uses a small amplitude sinusoidal voltage around the OCP value and the electrochemical current is measured at certain values of frequency. The phase shift is also measured. It is, also, called an Electrochemical Impedance Spectroscopy (EIS) and it can categorize the corrosion process of a system using the response of analogue circuit model to determine the corrosion parameters. Usually, it is applied in the interfaces of different materials such as coatings.
AC voltage and current have magnitudes and directions and the corresponding impedance is considered to be vector as a function of frequency “Z(ω)” which consists of real “Z'(ω)” and imaginary “Z"(ω)” impedance components. However, there is a phase shift (φ) between the applied potential and the recorded current due to the charging process.
The electrical double layer (EDL), shown in the following Error! Reference source not found., represents the corrosion (oxidation) for uncoated metal which takes place in the metal-electrolyte interface. Metal ions (positively charged) will go into the solution causing negative charges on the metal surface. Although water molecules can be diffused away from the metal surface, the negative charges of the surface will attract other positive and negative ions causing a change in the chemical composition of the bulk solution. The electrolyte layer that has water molecules will establish the electrical double layer (EDL).
EDL for metal in an electrolyte.
The EDL can be modeled by an analogous electrical circuit composed of a resistor (R) and a capacitor (C) as shown in the following Figure. In the Nyquist curve, Rs refers to the solution resistance, while Rct is the corrosion resistance or (charge transfer resistance) of the system which is the charge transfer resistance.
Circuit model for EDL.
More information can be obtained clearly from Bode diagrams since the solution resistance (Rs) can be determined from the high frequency domain, while the low frequency domain determines the summation of both solution resistance and corrosion resistance (Rct + Rs).
Two-time constants of AC spectra can be obtained in coated materials when the water ions and other corrosive ions penetrate thorough this coating forming a new electrolyte interface and affecting its dielectric properties. The ion movement will be restricted by the coating morphology producing coating resistance or pore resistance. This represents the first time constant due to coating resistance (RC, CC) in the high frequency region, while the EDL represents the second time constant for the low frequency region. The corrosion mechanism that has two-time constants will be represented by two semicircles on the Nyquist plot for low density poly ethylene (LDPE) coated with red iron oxide. The electrical circuit model for two-time constants is similar to the previous one but adds the effect of the coating response as shown in the following Figure.
Circuit model for two-time constant system
Regarding the AC impedance model, several attempts have been made to describe the circuit model of the electrochemical system of ceramic coatings. The variation in the proposed circuit models could be attributed to the physical representation of the corrosion process the coatings. For example, Wang et al., (2009) used an equivalent circuit to study the corrosion performance of PEO coating deposited on Q235 carbon steel in 3.5% NaCl solution where Rs, Rp and Rb represent resistance of the solution, resistance of the outer porous layer and resistance of the inner compact layer respectively. However, Qb is the constant phase element of the inner compact layer, while Qp is the constant phase element of the outer porous layer. It was found that corrosion protection of the coating was largely improved since the polarization resistance increased from 1.169×103 ΩNaN2 for the Q235 carbon steel to 5.143×103 ΩNaN2 for the coating.
Equivalent circuit of substrate / PEO coating system.
[Source: (Wang et al., 2009)]
Bode plots of uncoated and coated Q235 alloy in 3.5% NaCl solution (a) uncoated; (b) coated. [Source: (Wang et al., 2009)]
Another representation of the AC circuit model for PEO coating performed on AM50 magnesium alloy by Liang et al., (2009) in silicate electrolyte solution (Si-PEO) and phosphate electrolyte solution (P-PEO). It was assumed that quite a lot of number of micro pores exists across PEO coating where the corrosive electrolyte reached the substrate causing the formation of corrosion products (magnesium hydroxide). So, the following circuit parameters were used to fit the AC impedance data. Rs, Rp and Rf represent the solution resistance, porous outer layer resistance and inner layer/interface resistance respectively. Also, constant phase element was used to consider the effect of surface irregularities where CPEp represents the constant phase element of the porous outer layer and CPEf represents the constant phase element of the inner layer/interface.
Figure Error! No text of specified style in document..1: AC circuit model for PEO coating on Mg alloy.
[Source: (Liang et al., 2009)]
The impedance plots are shown in the following Figure where it was found that inner layer/interface resistance (Rf) of Si-PEO was higher than porous outer layer resistance (Rp) which indicates that the inner layer has the main effect to resist corrosion. Rp and Rf decreased with the immersion time indicating that the penetration of the corrosive solution through the oxide coating of the outer layer and it reached the inner layer. In case of the P-PEO, there was a significant decrease of both Rp and Rf which was due to the permeation of electrolyte through the defects and also the possible failure of the oxide coating causing localised corrosion on Mg substrate.
Nyquist (top) and Bode (bottom) plots in in 0.1M NaCl solution for coated AM50 alloy specimens by (a and b) PEO coating in silicate electrolyte, (c and d) PEO coating in phosphate electrolyte solution. [Source: (Liang et al., 2009)]
Although there is no agreement in the physical representation of the corrosion process of PEO, Barik et al., (2005), proposed an AC impedance circuit model to investigate the corrosion behaviour of PEO coatings on 6082 aluminium alloy as shown in the following Figure. It consists of solution resistance Rs, the coating pore resistance Rpore, the coating capacitance Ccoating, the charge transfer resistance Rct, and the double layer capacitance Cdl.
PEO coating with proposed AC circuit model.[Source: (Barik et al., 2005)]
It is assumed that the coating/substrate interface will be controlled by an activation process as suggested by (Barik et al., 2005) for PEO coatings and are composed of two depressed semi-circles as showing in the following Figure.
AC impedance of aluminium and PEO coating.
[Source: (Barik et al., 2005)]
References :
Wang, Y., Z. Jiang, et al., (2009). "Microstructure and corrosion resistance of ceramic coating on carbon steel prepared by plasma electrolytic oxidation." Surface and Coatings Technology 204(11): 1685-1688.
Liang, J., P. B. Srinivasan, et al., (2009). "Electrochemical corrosion behaviour of plasma electrolytic oxidation coatings on AM50 magnesium alloy formed in silicate and phosphate based electrolytes." Electrochimica Acta 54(14): 3842-3850.
Barik, R. C., Wharton, J. A., Wood, R. J. K., Tan, K. S. & Stokes, K. R. (2005) Erosion and erosion-corrosion performance of cast and thermally sprayed nickel-aluminium bronze. Wear, 259, 230-242.
Comment 6
Table 3 - Please introduce the errors
Authors Reply:
The errors were introduced in Table 3 (check the modified manuscript), except the corrosion current density because the corrosion current densities for the materials tested in this work were determined from the logarithmic scale of the current density in the anodic polarization curves as shown in the following graphs from for Al, HA, PEO and PSC respectively.
Determination of corrosion current density for Al substrate.
Determination of corrosion current density for HA.
Determination of corrosion current density for PEO.
Determination of corrosion current density for PSC.
Thanks for your guidance and I hope to cooperate with you in the near future.
Best Regards
Sincerely yours,
Essam R. I. Mahmoud (Corresponding author)
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This work is too interesting; the authors did a very good work. This work may be accepted after considering some important/major points for revision.
The main industerial/engineering application of such alloys and surface coating technique is not clear in your work. Should be indicated clearly through your texts.
The main objective and long term vision is not clear in this manuscript. Why you have selected such alloys (6082 Aluminum) for your study. All of these points should be clear in your text.
The Evans Diagrams did not clear the cathodic polarization, why? should be identified the discussions in your texts.
What about the passivation behavior (characteristics of such layers and its effect on the surface coating of such alloys investigated. What about the possibility of paasive layer breakdown, regarding to the polarization curves (E,I).
Figure 2 is not discussed well. What do you want to tell by this Figure. The authors should explain clearly the importance of such phases and its effect in this work.
Figures 12, 16, and 17 have less quality to indicate the authors point of view. Should be replace by SEM micrographs or qualitative ones.
If there is any mechanical and or agressive enviornmental effects (Températures, etc.) on such coating materials, what will be its effect on the corrosion characteristisc of Aluminum surface. May depend on the nature of working conditions of such alloys? Should be clear in your text.
Author Response
Dear Prof. Editors/ Reviewers
I thank you very much for your concern about my paper (Ref. No.: processes-386214) titled “Corrosion behavior of 6082 Aluminum Alloy Surface after Coating with Different Ceramic Coating processes" and appreciate your valuable comments on my work. Kindly, please find my replying on your comments in the following points:
For Editor: the paper title was modified to “Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy”
Reviewer #2:
Comment 1
This work is too interesting; the authors did a very good work. This work may be accepted after considering some important/major points for revision.
Authors Reply:
Thank you very much for your accurate and valuable evaluation. The necessary modifications will be done on the
manuscript according to your comments.
Comment 2
The main industrial/engineering application of such alloys and surface coating technique is not clear in your work. Should be indicated clearly through your texts.
Authors Reply:
The applications of aluminum alloy 6082 was added to the beginning of Introduction Section as" Aluminium alloy 6082 has the highest strength of the 6000 series alloys, and it used in many highly stressed applications such as aeronautics, trusses, bridges, transport applications, cranes and aerospace industries [1]." This added paragraph is highlighted by red color in the text.
Comment 3
The main objective and long term vision is not clear in this manuscript. Why you have selected such alloys (6082 Aluminum) for your study. All of these points should be clear in your text.
Authors Reply:
The selection/application of aluminum alloy 6082 was added in the text as mentioned in the previous comment #2. Also, the sentences “As a result, relatively poor corrosion resistance often decreases the lifetime of the aluminum alloy components. Thus, some surface engineering techniques on aluminum alloys would be indispensable to their applications.” was added to the end of the first paragraph in Introduction Section.
Comment 4
What about the passivation behavior (characteristics of such layers and its effect on the surface coating of such alloys investigated. What about the possibility of passive layer breakdown, regarding to the polarization curves (E,I).
Authors Reply: Aluminium is a passive material which can naturally form an oxide dense layer to give corrosion protection as the potential increases. However, the corrosion potential of the metal is achieved (U2) which causes re-dissolution of the passive film (See the following figure). The metal will re-passivate due to the increase of the potential and the oxide film will grow (U3). At this stage, a conventional anodizing will take place. However, higher potential value is further applied to the path (exceeding the breakdown potential) which differentiates PEO process from the traditional hard anodizing process. At voltage stage (U4), the micro-discharges will occur in the oxide film due to dielectric breakdown causing movements between ions and atoms in the alkaline solution. After U5, the powerful arcs will be produced due to the transformation of arc micro-discharges where the plasma-chemical reactions will occur. Consequently, the oxide film will be formed on the metal and α-Al2O3 and γ-Al2O3 will be produced (Curran, 2005). Figure Error! No text of specified style in document..1: Current-voltage plot during PEO process. [Source: (Curran, 2005)]
Curran, J. A. and T. W. Clyne (2005). "Thermo-physical properties of plasma electrolytic oxide coatings on aluminium." Surface and Coatings Technology 199(2-3): 168-176.
Comment 5
Figure 2 is not discussed well. What do you want to tell by this Figure. The authors should explain clearly the importance of such phases and its effect in this work.
Authors Reply:
Figure 2 shows the microstructure of the substrate 6082 –T6 aluminium alloy in polished and etched conditions. The micrographs revealed particles of different sizes distributed within the Al matrix. These particles may be the well-known intermetallics (β-Al5FeSi, Mg2Si, Al9Mn3Si, Mg2Si, α-Al(FeMn)Si) shown in this type of Al alloy. These intermetallics support and strengthen the matrix. For that the alloy 6082 is consider one of the highest strength of the aluminum alloys. This explanation was clearly mentioned in the beginning of the Macro/Microstructure Analysis section.
Comment 6
Figures 12, 16, and 17 have less quality to indicate the authors point of view. Should be replace by SEM micrographs or qualitative ones.
Authors Reply:
The samples of this work were used for erosion test. Unfortunately, most of the samples already damaged. Only the optical macrographs are available. It shows only the macro-features of the surface after corrosion tests. We will try to provide more clear images to the editor.
Comment 7
If there is any mechanical and or agressive enviornmental effects (Températures, etc.) on such coating materials, what will be its effect on the corrosion characteristisc of Aluminum surface. May depend on the nature of working conditions of such alloys? Should be clear in your text.
Authors Reply:
We totally agree with your comment. The effect of temperature and the erosion/corrosion behavior after exposing the sample to high speed water containing sand particles will be discussed in a separate paper.
Thanks for your guidance and I hope to cooperate with you in the near future.
Best Regards
Sincerely yours,
Essam R. I. Mahmoud (Corresponding author)
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript is interesting however, it has a lot of drawback in respect to soundness of results and discussion. It can be considered for publication if authors will answer and improve the quality of manuscript. My suggestions are as below:
1. Abstract section need to be rewrite specially the comment about impedance result. In lines 22-24 cannot corroborate as obtained EIS result.
2. Is the process adopted for electrochemical studies follow any standard or only as convenient to authors? I suggest to authors to follow a specific standard for electrochemical studies. It is very serious issue for electrochemical study. If authors did not follow the standard, then this manuscript must be rejected.
3. Figure 1 is hazy and not clear. What are the authors want to show here?
4. Figure 2 is not required to show here. There is no meaning. Authors only need to describe the process for polishing of substrate before deposition of coating.
5. It requires to check English by native English speaker. English is poor quality.
6. Experimental section need to be elaborate in details. Is has very weak explanation and details of experiment performed by the authors. This section is not clear. There are no details of electrochemical studies parameters selected along with details about the instrument for SEM, XRD and optical microscope. What was the range to scan the XRD data?
7. Figure 3 is poor quality. It does not show any clear properties/morphology of coatings.
8. Authors are writing some time AH and sometime HA. Please make it consistent throughout the manuscript.
9. I suggest to authors to provide the hardness, bond strength and particle size of each coatings.
10. There is no EDS result in the manuscript while authors are describing about this result in lines 158-164.
11. I suggest to authors to put all subfigures of Fig. 4 in one plot and compare them.
12. If material is amorphous then there will be no peaks observed. Then how authors mention this phenomenon in line 166. While by seeing the Fig. 4a and b, both show intense peak of Al. What is the difference in Fig. 4a and Fig. 4b? There is no meaning while it is confusing to the readers.
13. For Fig. 5, my same opinion as 11.
14. Is there any standard to perform Mass Loss from Polarization Tests?
15. For the first 30 s to measure the OCP does not make any sense for corrosion point of view. Thus, Fig. 6 does nor infer any information.
16. In line 209, %3.5 is typo mistake.
17. AL must be Al in Fig .6.
18. How does it possible that PEO coating show positive OCP? I suggest to authors to recheck it.
19. For Fig.8, please refer 11.
20. There is no fitted data of EIS and electrochemical circuit.
21. I suggest to authors to rewrite the manuscript. It has full of drawback. Results are not properly explained and lack of scientific contribution. If authors thoroughly revise the manuscript, then I can consider for further round of review. In its present form, it cannot be accepted for publication.
Author Response
Dear Prof. Editors/ Reviewers
I thank you very much for your concern about my paper (Ref. No.: processes-386214) titled “Corrosion behavior of 6082 Aluminum Alloy Surface after Coating with Different Ceramic Coating processes" and appreciate your valuable comments on my work. Kindly, please find my replying on your comments in the following points:
For Editor: the paper title was modified to “Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy”
Reviewer #3:
Comment 1
The manuscript is interesting however, it has a lot of drawback in respect to soundness of results and discussion. It can be considered for publication if authors will answer and improve the quality of manuscript.
Authors Reply:
Thank you very much for your accurate and valuable evaluation. The necessary modifications will be done on the manuscript according to your comments.
Comment 2
Abstract section need to be rewrite specially the comment about impedance result. In lines 22-24 cannot corroborate as obtained EIS result.
Authors Reply:
The abstract has been modified and also aligned with other reviewers’ comments to be “Aluminium alloys cannot be used in aggressive corrosion environments application. In this paper, three different surface coating technologies were used to coat the 6082-T6 aluminum alloy to increase the corrosion resistance, namely Plasma Electrolytic Oxidation (PEO), Plasma Spray Ceramic (PSC) and Hard Anodizing (HA). The cross-sectional macrostructure analysis revealed that HA coating was less uniform compared to other coatings. PEO coating was well adhered to the substrate despite the thinnest layer among all three coatings, while the PSC coating has an additional loose layer between the coat and the substrate. XRD analysis revealed crystalline alumina phases in PEO and PSC coatings while no phase was detected in HA other than an aluminum element. A series of electrochemistry experiments were used to evaluate the corrosion performances of these three types of coatings. Generally, all three-coated aluminium showed better corrosion performance. PEO coating has no charge transfer under all Inductive Coupled Plasma (ICP) tests, while small amounts of Al3+ were released for both HA and PSC coatings at 80°C. The PEO coating showed the lowest corrosion current density followed by HA and then PSC coatings. The impedance resistance decreased as the immersion time increased, which indicated that this is due to the degradation and deterioration of the protective coatings. The results indicate that the PEO coating can offer the most effective protection to the aluminium substrate as it has the highest enhancement factor under electrochemistry tests compared to the other two coatings.”
Comment 3
Is the process adopted for electrochemical studies follow any standard or only as convenient to authors? I suggest to authors to follow a specific standard for electrochemical studies. It is very serious issue for electrochemical study. If authors did not follow the standard, then this manuscript must be rejected.
Authors Reply:
The condition we used in the electrochemical analysis is similar to oil and gas sector environments. Our main target in this work is to introduce sufficient data about coated aluminum ally that can prove to be effective under oil and gas environments to replace the steel alloys. The subject of surface engineering, especially in oil and gas industry, is considered to be one of the most important current research activities in our area (Gulf Area) that require further investigations in reducing materials degradation to meet the continuous demand in this sector. Regarding the international standards, the vast majority of our work was very close to the regulations of “ASTM G 102, Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements”.
Comment 4
Figure 1 is hazy and not clear. What are the authors want to show here?.
Authors Reply:
Figure 1 shows the sample holder and its assembly steps that used for electrochemistry tests which has been designed specially to allow testing the materials in the more convenient way. This holder allows both faces of the sample to be tested without using a resin. We tried to modify the figure to be clear (See in the manuscript).
Comment 5
Figure 2 is not required to show here. There is no meaning. Authors only need to describe the process for polishing of substrate before deposition of coating.
Authors Reply:
Figure 2 shows the microstructure of the substrate 6082 –T6 aluminium alloy in polished and etched conditions. The micrographs revealed particles of different sizes distributed within the Al matrix. These particles may be the well-known intermetallics (β-Al5FeSi, Mg2Si, Al9Mn3Si, Mg2Si, α-Al(FeMn)Si) shown in this type of Al alloy. These intermetallics support and strengthen the matrix. For that the alloy 6082 is consider one of the highest strength of the aluminum alloys. This explanation was clearly mentioned in the beginning of the 3.1 macro/Microstructure Analysis section.
Comment 6
It requires to check English by native English speaker. English is poor quality.
Authors Reply:
The whole paper was carefully revised by an English native reviewer and the necessary corrections were done.
Comment 7
Experimental section need to be elaborate in details. Is has very weak explanation and details of experiment performed by the authors. This section is not clear. There are no details of electrochemical studies parameters selected along with details about the instrument for SEM, XRD and optical microscope. What was the range to scan the XRD data?.
Authors Reply:
We tried to re-write the part of experimental section to answer your questions in your comment. Please check the revised modified version.
Comment 8
Figure 3 is poor quality. It does not show any clear properties/morphology of coatings.
Authors Reply:
Figure 3 shows the cross-sectional macrostructures of the three coatings. The figure shows the different main two layers thickness in the cross-sectional view of the coating which are inner and outer layers. each original image was clear. The quality of the images became poor when we collect the four images together in one figure. We will try to solve it.
Comment 9
Authors are writing some time AH and sometime HA. Please make it consistent throughout the manuscript.
Authors Reply:
We checked the whole paper and fixed it as “HA”.
Comment 10
I suggest to authors to provide the hardness, bond strength and particle size of each coatings.
Authors Reply:
These data were not available for the authors.
Comment 11
There is no EDS result in the manuscript while authors are describing about this result in lines 158-164.
Authors Reply:
We have the EDS spectra for the three coatings. The number of existing figures of this paper are 20. It is considered too much. We decided to not show some of the figures as an image and shows its results. One of these figures was the EDS spectra.
EDS for HA
EDS for PEO
EDS for PSC
Comment 12
I suggest to authors to put all subfigures of Fig. 4 in one plot and compare them.
Authors Reply:
You mean the XRD spectra for the three coating. Most of the detected phases were alumina phases (α-Al2O3, γ-Al2O3), especially for PEO and PSC. It become overlapped and the resulted figures will be confused. For HA, no phases detected apart from aluminium element.
Comment 13
If material is amorphous then there will be no peaks observed. Then how authors mention this phenomenon in line 166. While by seeing the Fig. 4a and b, both show intense peak of Al. What is the difference in Fig. 4a and Fig. 4b? There is no meaning while it is confusing to the readers.
Authors Reply:
For hard anodizing (HA) layer, the coating is amorphous in nature. For that reason, no oxide phases were detected. Only the aluminum element was detected as shown in Fig. 4 (a) and its zoomed spectra in Fig. 4 (b). these aluminum peaks come from the substrate beneath the layer. We showed zoomed spectra Fig. 4(b) to be sure there was no other phases except Al. For the other coatings; PEO and PSC, The main phases detected are alumina phases (α-Al2O3, γ-Al2O3) and aluminum element as shown in Figs. 4(c) and (d).
Comment 14
For Fig. 5, my same opinion as 11.
Authors Reply:
What we got from your comment is to summarize the data in one columned figure. This is a great idea. In the same time, the features of the curves also very important. For example, HA coating shows sharp increase in the current for the first 1200 seconds then the current stabilized and steadily increased with some fluctuation for the rest of the test period. However, the PEO coating shows a gradual increase of the current density throughout the test period without any sudden increase of the current. For PSC coating, there is no stability of the current as high variation of the curve occurred during the 24 hours polarization test and the current was significantly high compared to the other two coatings.
Comment 15
Is there any standard to perform Mass Loss from Polarization Tests?.
Authors Reply:
The mass loss at the electrode was calculated using the Using Faraday's Law rule:
Where:m is the mass of material lost at the electrolyte (g).Q is the charge passed through the substance (C).F is Faraday’s constant (= 96485 C mol-1).M is the molar mass of the substance (g/mol).z is the valence number of ions of the substance.
Comment 16
For the first 30 s to measure the OCP does not make any sense for corrosion point of view. Thus, Fig. 6 does nor infer any information.
Authors Reply:
The OCP measurements were carried out for 30s to find the starting OCP values for all three coating materials. PEO coating has the highest starting OCP value with -0.048V while PSC coating has the most negative OCP value of about -0.76V.
According to many references, a high OCP value refers to a better corrosion protection, which indicates the enhancements of PEO coating in the corrosion performance.
Comment 17
In line 209, %3.5 is typo mistake.
Authors Reply:
Yes, it was fixed to be 3.5%.
Comment 18
AL must be Al in Fig .6.
Authors Reply:
Yes, it was fixed to be “Al” instead of “AL” in Fig. 6.
Comment 19
How does it possible that PEO coating show positive OCP? I suggest to authors to recheck it.
Authors Reply:
Since the PEO has highly dense oxide layer, the OCP started with negative value then due to current fluctuating at the start, it increased to relatively small positive OCP then decreased until reaching similar value of the aluminium substrate which means complete movement of the ions from the substrate to the upper part of the PEO coating.
Comment 20
There is no fitted data of EIS and electrochemical circuit.
Authors Reply:
Fitting AC data using circuit model for Al
The AC data for the aluminium alloy was fitted using ZView software and the Randles circuit model shown in Figure . This circuit model has been used to represent the corrosion process for the aluminium surface. Rs refers to the uncompensated resistance of the solution between the working electrode (aluminium surface) and the reference electrode (Ag/AgCl). Rct refers to the charge transfer resistance which is the resistance of the ions movement at the electrode/solution interface. The double layer capacitor, Cdl, describes the electrode capacitance. It is noticed that the equivalent circuit model did not fit the AC impedance data for the aluminium in in the first day of immersion (Figure ) while the fittings are much better from Day 1 to Day 10. This could be due to the interaction of the aluminium ions with the electrolyte at the passive film interface and causes scattered data in the low frequency region at initial period of immersing the sample in the 3.5% NaCl solution. Figure shows the AC impedance spectra for the aluminium for the last day of immersion (Day 10) where good fit of the data can be obtained. It is clearly shown that the aluminium substrate has only one time constant throughout the test period. Figure shows the values of the total resistance and the capacitance obtained from the AC data over the immersion time for the aluminium substrate. The total resistance (Rtot = Rs+ Rct) seems to be fluctuating over the immersion time which indicates the subsequent of formation and dissolution of the aluminium passive film.
Figure 1: Randles circuit model used to fit the impedance data for Al substrate.
(b) |
Figure 2: Fitted data for Al coating at day 0 (a) Nyquist plot, (b) Bode magnitude plot and (c) Bode phase plot.
(c) |
Figure 3: Fitted data for Al coating at day 10 (a) Nyquist plot, (b) Bode magnitude plot and (c) Bode phase plot.
Figure 4: Time dependence of the Rtot and CEDL for Al surface after different exposure times.
Fitting AC data using circuit model for HA
Many trials have been made to develop an equivalent circuit models to fit the AC spectra of HA coating. However, no good fit can be obtained using conventional circuit models. Firstly, the equivalent circuit model (Figure ) was used where Rs and Rc account for the resistance of the solution and the coating respectively. Rct represents the resistance to transfer of charge from the HA coating to the substrate. CPE1 and CPE2 represent the constant phase element of coating and the electrical double layer respectively while CPE3 represents the mass transfer and the ionic charges distribution around the unprotected metal substrate under the coating. Figure shows the fitted AC data for Day 0 where two peaks can be distinguished, corresponding to two time constants. However, this model did not fit the AC data accurately for all periods of time as shown in the phase plots for both Day 0 and Day 10 in Figure (c) and Figure (c) respectively.
Figure 5: Equivalent circuit model to fit the AC impedance of HA.
(b) |
Figure 6: Fitted data for HA coating at day 0 (a) Nyquist plot, (b) Bode magnitude plot and (c) Bode phase plot.
(c) |
Figure 7: Fitted data for HA coating at day 10(a) Nyquist plot, (b) Bode magnitude plot and (c) Bode phase plot.
The second equivalent circuit model used to fit the AC spectra of HA is shown in Figure . Similar to the previous model, Rs and Rc account for the resistance of the solution and the coating respectively. Rct represents the resistance to transfer of charge from the HA coating to the substrate. CPE1 and CPE2 represent the constant phase element of coating and the electrical double layer respectively. This model was modified by adding a third constant phase element (CPE3) to represent the mass transfer and the ionic charges distribution around the unprotected metal substrate under the coating. Figure shows the fitted AC data where two peaks can be distinguished, corresponding to two time constants. Although this model has better enhancements compared to the previous one, the fitted line did not match well with AC impedance. This suggests that the corrosion process for this coating is more complicated and needs some extra elements to represent the more complicated physical process. It would appear from the 45º line that diffusion processes are taking place and letting a Warburg elements did not lead to a better fit. The Nyquist plot, therefore, is left unlimited and is denoted as having high impedance with some diffusion element.
Figure 8: Equivalent circuit model to fit the AC impedance of HA coating.
(a) |
Figure 9: Fitted data for HA coating at day 0 (a) Nyquist plot, (b) Bode magnitude plot and (c) Bode phase plot.
(c) |
Fitting AC data using circuit model for PEO
There is a decrease in the depressed semi-circle radii between the first day and the last day of the experiment as shown in Figure and Figure respectively. The total corrosion resistance decreased rapidly from about 45000 ΩNaN2 at Day 0 to around 1000 ΩNaN2 at Day 1 then it kept fluctuating slightly around this value till the end of the immersion period (Figure ).
(c) |
Figure 10: Fitted data for PEO coating at day 0.
(c) |
Figure 11: Fitted data for PEO coating at day 10.
Figure 12: Time dependence of the Rtot and CPE2 for PEO coating after different exposure times.
Fitting AC data using circuit model for PSC
The results for PSC are shown in Figure and Figure for the first day and Day 10 of the immersion period respectively. Although there is no significant change in the arc radius of the Nyquist plot of PSC at initial immersion and after the full period of immersion test, the total resistance was fluctuating between these two end points as shown in Figure . The increase of the resistance between day 2 and day 5 corresponds to the formation of the corrosion products at the coating/substrate interface that initiated due to ions transfer in the pores regions of PSC surface. The resistance and phase constant element were fluctuating during the period of the test (Figure ) which indicate that part of the PSC coting was delaminated.
(c) |
Figure 13: Fitted data for PSC coating at day 0.
(c) |
Figure 14: Fitted data for PSC coating at day 10.
Figure 15: Time dependence of the Rtot and CPE2 for PSC coating after different exposure times.
Comment 21
I suggest to authors to rewrite the manuscript. It has full of drawback. Results are not properly explained and lack of scientific contribution. If authors thoroughly revise the manuscript, then I can consider for further round of review. In its present form, it cannot be accepted for publication.
Authors Reply:
We have reviewed the manuscript carefully and modified the necessary revision to improve the presentation, quality and to remove any misunderstanding that reader might get from the original manuscript. The revised manuscript is also aligned with the comments and observations suggested by other reviewers. We believe that it is now presented in much better manner.
Thanks for your guidance and I hope to cooperate with you in the near future.
Best Regards
Sincerely yours,
Essam R. I. Mahmoud (Corresponding author)
Author Response File: Author Response.pdf
Reviewer 4 Report
The authors have done a very good and valuable work in this field; and the writing is good as well. However some issues need to be resolved prior to acceptance for publishing.
The title sounds a little too general as compared to the contents. The title may be changed as (but not limited to) "Experimental studies on corrosion behaviors of ...". Note that "behavior" should be plural here; and keep the grade of aluminum to be consistent "6082-T6" where "T6" has been missed somewhere in the manuscript; please check through the manuscript and fix them all.
Line 17 and 18, "performance" should be plural here. Please check through the manuscript for the same problems and fix them all.
Line 19, add an article "a" before "crystalline".
Line 19, "structure" should be changed to "microstructure" in this case. Please check through the manuscript for the same problems and fix them all.
Line 20, "barrier" should be changed to "protection" in this case. Note that "barrier" for electrolyte, and "protection" for substrate. Please check through the manuscript for the same problems and fix them all.
Line 29, "an element" should be changed to "a metal" in this case. Because what is talked about is a piece of aluminum metal instead of aluminum element.
Line 32, "like" can be changed to "such as" in this case.
Line 37, please check the logic in the sentence "...While ...it..." which sounds not logical.
Line 37, delete "the" before "temperature".
Line 38, what "...takes ...tool..." mean here?
Line 40, "life" can be changed to "lifetime" in this case. Please check through the manuscript for the same problems and fix them all.
Line 42, "research" should be plural in this case.
Line 42, in "...material's...", "...'s..." can be deleted in this case. Please check through the manuscript for the same problems and fix them all.
Line 43, "it" should be deleted here; or add a semicolon ";" before "...and it...".
Line 46 to 47, "costs" can be moved before "replacement and..." and changed as "...the costs in (or of)...".
Line 54, add "as" after "such".
Line 58, please check the use of "in order for".
Line 61, "in addition of" should be changed to "in addition to".
Line 64, "it" should be deleted here; or add a semicolon ";" before "...and it...".
Line 68, "to be" can be deleted in this case.
Line 72, "impact" should be changed to "impacting".
Line 80, "more than" can be changed to "as compared to" in this case.
Line 81, "film" and "coating" are repeated here, please delete one of them. Please check through the manuscript for the same problems and fix them all.
Line 94, please check if the thickness is 10 mm? it sounds too thick.
Line 96, please check the use of semicolon ";" in this case.
Note that there are many misused semicolons ";" in this manuscript including in the captions of figures and tables, Please check through the manuscript for the same problems and fix them all.
Line 98, please check the writing "M3...to make a hole..." that is not professional.
Lines 98 to 101, you do not necessary to tell where the samples were sent. You can just say the samples were outsourced for what processes...
Line 100, the quotation marks are not necessary here. Please check through the manuscript for the same problems and fix them all.
Line 104, "...the more..." can be changed to "...a more...".
Note that in this manuscript, "Fig. 1" and "Figure 1" have been used. Please make them in a consistent format throughout the manuscript, to make it easier for the readers to search for them.
Line 105, "a" should be deleted before "resin".
Line 107, please check if "from" should be changed to "to" in this case.
Line 109, add a space in "24hours". Please check through the manuscript for the same problems and fix them all.
Line 112, please check there are "were" and "was".
Note, in this manuscript, "twenty-four hours", "24 hours", "ten days" and "10 days" have been used. Please make them in a consistent format throughout the manuscript.
Line 113, please check the sentence "because all the coatings..." for logical problem.
Line 114, "in" should be deleted.
Line 115, "...at..." should be changed to "...in a..."; and add "...at a given..." before "scan rate".
Line 116, "...involve..." should be changed to "...are involved in...".
Line 118, please check the symbol "icorr" should be corrosion current density rather than "corrosion resistance".
Line 119 to 120, please check the sentence "...one passes..." that does not make sense.
Line 124, what is "the sample perturbation" here?
Line 127 to 128, more parameters can be introduced for the XRD analysis.
Figure 1 may be not value added to show the details of the electrochemistry sample holder. Because it not a unique design. Instead, you just need to provide by explaining what the exposure area or diameter is, which is needed in the calculation of the corrosion current density. So, I suggest deleting this figure, if so please remember to reorganize the other figures number in captions and text.
Line 149, "...followed by..." should be changed to "...followed with..." in this case. Please check through the manuscript for the same problems and fix them all.
Line 153, the comma "," before "it also..." should be changed to a semicolon ";" in this case.
In the captions of Figure 3, please indicate what types (OM or SEM) of images for (a) to (c).
Reference [48] has been not shown between [47] and [49]. Please check the make sure all the references are properly numbered and in a order throughout the manuscript.
Line 167, why use "believed to be"?
Line 168, add "is" before "shown".
Line 168, "literature" should be plural in this case.
Line 191, "for" should be changed to "in" in this case.
Line 192, "of" can be changed to "in"; "the" can be deleted before "current density".
Line 198, how did you know the high porosity? you may need to introduce this in Section of "Materials and Methods". "also" can be deleted.
Line 201, "electrochemistry" can be changed to "electrochemical" in this case.
Line 207, add "the" after "all".
Line 208, what are "materials" here? did you mean "coatings"?
Line 216, "corrosion" should be changed to "anticorrosion" in this case.
In Figure 6, the horizontal axis and its title do not stay together, one is on the top and the other is on the bottom. Please check through the manuscript for the same problems and fix them all.
In this manuscript some tenses have been not properly used, for example the present perfect tense (have done...). Please check throughout the manuscript for such issues and accordingly adjust all of them to be the right tenses.
Line 225, delete "the" before "coating thickness".
Line 225 to 228, the discussion and statement about the correlation between coating thickness, coating porosity and electrochemical resistance need references to support your work. One of the good references is as below:
The Roles of Diffusion Factors in Electrochemical Corrosion of TiN and CrN (CrSiCN) Coated Mild Steel and Stainless Steel, (https://doi.org/10.1002/9781118356074.ch7)
Line 244 to 245, add "the" after "all".
Line 245, suggest adding "systems" after "materials". Since these coatings are kinds of materials systems. Please check through the manuscript for the same problems and fix them all.
Line 259, please check the sentence "by extrapolating ...OCP value." for grammatical problems.
Line 261, please check if "in" should be "is" or "was"?
Line 275, please check the sentence "...has...were..." for grammatical problems.
About the current density, different formats of unit have been used. Please check throughout the manuscript and make them all in a consistent format, including those in figures.
Line 296 to 297, "phase angle" is mentioned. However, no angle is found in Figures 13 and 14. Please check and make a correction accordingly.
Line 299, "eye" should be plural in this case.
In Figures 13, 14, 19, and 20, some of images do not show units for the accordingly axis, and some of numbering systems are not in a consistent format. Please check through the manuscript for the same problems and fix them all.
Line 316, add "the" before "dissolution".
Line 316 to 317, your discussion and statement about coating thickness, porous and electrolyte ion movement, need references to support your work. One of the good references is as below:
The Roles of Diffusion Factors in Electrochemical Corrosion of TiN and CrN (CrSiCN) Coated Mild Steel and Stainless Steel, (https://doi.org/10.1002/9781118356074.ch7)
Line 320, again, please check the reference [48] for it proper order in the manuscript.
Line 347, "fitted" should be changed to for example "combined" ...
Line 351, what "Thin" mean here?
Line 352, "two time constants" may be written as "two-time constants" so that have a consistent format with "one-time constant".
Line 355, add a semicolon ";" after "obtained" otherwise delete "they".
Line 357 to 358, please check the sentence "...is taking place ...properties..." for grammatical or logical problems, why to the properties?
Line 358 to 360, your discussion and statement need references to support your work. One of the good references is as below:
The Roles of Diffusion Factors in Electrochemical Corrosion of TiN and CrN (CrSiCN) Coated Mild Steel and Stainless Steel, (https://doi.org/10.1002/9781118356074.ch7)
Line 364, please check the use of "uptake" in this case.
Line 374, add "the" before "three types of...".
Line 383, please check the sentence "...is taking place ...properties..." for grammatical or logical problems, why to the properties? also this sentence is copied from that in Line 357, repeating sentences should be avoided.
Line 384, add "the three" after "All".
Author Response
Dear Prof. Editors/ Reviewers
I thank you very much for your concern about my paper (Ref. No.: processes-386214) titled “Corrosion behavior of 6082 Aluminum Alloy Surface after Coating with Different Ceramic Coating processes" and appreciate your valuable comments on my work. Kindly, please find my replying on your comments in the following points:
For Editor: the paper title was modified to “Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy”
Reviewer #4:
Comment 1
The authors have done a very good and valuable work in this field; and the writing is good as well. However some issues need to be resolved prior to acceptance for publishing.
Authors Reply:
Thank you very much for your accurate and valuable evaluation. The necessary modifications will be done on the manuscript according to your comments.
Comment 2
The title sounds a little too general as compared to the contents. The title may be changed as (but not limited to) "Experimental studies on corrosion behaviors of ...". Note that "behavior" should be plural here; and keep the grade of aluminum to be consistent "6082-T6" where "T6" has been missed somewhere in the manuscript; please check through the manuscript and fix them all.
Authors Reply:
We agree with your comment. the title was modified to be “Experimental studies on corrosion behaviors of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy”.
Comment 3
Line 17 and 18, "performance" should be plural here. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Yes, it was fixed through the whole text (7 times).
Comment 4
Line 19, add an article "a" before "crystalline".
Authors Reply:
Yes, it was fixed in the text.
Comment 5
Line 19, "structure" should be changed to "microstructure" in this case. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Yes, it was fixed in the text.
Comment 6
Line 20, "barrier" should be changed to "protection" in this case. Note that "barrier" for electrolyte, and "protection" for substrate. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Yes, it was fixed in the text.
Comment 7
Line 29, "an element" should be changed to "a metal" in this case. Because what is talked about is a piece of aluminum metal instead of aluminum element
Authors Reply:
Yes, it was fixed in the text.
Comment 8
Line 32, "like" can be changed to "such as" in this case.
Authors Reply:
Yes, it was fixed in the text.
Comment 9
Line 37, please check the logic in the sentence "...While ...it..." which sounds not logical.
Authors Reply:
The sentence was modified to be “The corrosion rate increases with increasing the temperature, and it decreases by increasing the angle of inclination”.
Comment 10
Line 37, delete "the" before "temperature".
Authors Reply:
Yes, it was fixed in the text.
Comment 11
Line 38, what "...takes ...tool..." mean here?.
Authors Reply:
The sentence was modified to be “Corrosion plays a significant role in human life and safety.”
Comment 12
Line 40, "life" can be changed to "lifetime" in this case. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Yes, it was fixed in the text.
Comment 13
Line 42, "research" should be plural in this case
Authors Reply:
Yes, it was fixed in the text.
Comment 14
Line 42, in "...material's...", "...'s..." can be deleted in this case. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Yes, it was fixed in the text.
Comment 15
Line 43, "it" should be deleted here; or add a semicolon ";" before "...and it..."..
Authors Reply:
Yes, it was fixed in the text.
Comment 16
Line 46 to 47, "costs" can be moved before "replacement and..." and changed as "...the costs in (or of)...".
Authors Reply:
Yes, it was fixed in the text.
Comment 17
Line 54, add "as" after "such".
Authors Reply:
Yes, it was fixed in the text.
Comment 18
Line 58, please check the use of "in order for".
Authors Reply:
The sentence was modified to “The applied electrical potential should be high enough to the plasma discharges and sparks to be formed and generate oxide films with relatively higher thickness.”
Comment 19
Line 61, "in addition of" should be changed to "in addition to".
Authors Reply:
Yes, it was fixed in the text.
Comment 20
Line 64, "it" should be deleted here; or add a semicolon ";" before "...and it...".
Authors Reply:
Yes, it was fixed in the text.
Comment 21
Line 68, "to be" can be deleted in this case.
Authors Reply:
Yes, it was fixed in the text.
Comment 22
Line 72, "impact" should be changed to "impacting".
Authors Reply:
Yes, it was fixed in the text.
Comment 23
Line 80, "more than" can be changed to "as compared to" in this case.
Authors Reply:
Yes, it was fixed in the text.
Comment 24
Line 81, "film" and "coating" are repeated here, please delete one of them. Please check through the manuscript for the same problems and fix them all
Authors Reply:
Yes, it was fixed in the text.
Comment 25
Line 94, please check if the thickness is 10 mm? it sounds too thick
Authors Reply:
It is right. The thickness was 10 mm.
Comment 26
Note that there are many misused semicolons ";" in this manuscript including in the captions of figures and tables, Please check through the manuscript for the same problems and fix them all.
Authors Reply:
We agreed with this observation and revised the manuscript accordingly.
Comment 27
Line 98, please check the writing "M3...to make a hole..." that is not professional.
Authors Reply:
The comment is totally right. It was a mistake. The sentence was modified as “For PEO samples, a 3 mm diameter hole was drilled in the aluminum substrates for the anode to be inserted in the sample…”.
Comment 28
Lines 98 to 101, you do not necessary to tell where the samples were sent. You can just say the samples were outsourced for what processes...
Authors Reply:
We believe that this additional information is useful for the researchers traying to replicate or do similar research. The purpose of mentioning the company name was not to glorify the company but to provide additional information and authenticity of our work. We decided to keep the names as mentioned in the original manuscript.
Comment 29
Line 100, the quotation marks are not necessary here. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
This has been corrected in the revised manuscript.
Comment 30
Line 104, "...the more..." can be changed to "...a more...".
Authors Reply:
Yes, it was fixed in the text.
Comment 31
Note that in this manuscript, "Fig. 1" and "Figure 1" have been used. Please make them in a consistent format throughout the manuscript, to make it easier for the readers to search for them.
Authors Reply:
The word “Figure” is used when the paragraph start with it and the word “Fig.“ is used when it is mentioned within the paragraph.
Comment 32
Line 105, "a" should be deleted before "resin".
Authors Reply:
Yes, it was fixed in the text.
Comment 33
Line 107, please check if "from" should be changed to "to" in this case.
Authors Reply:
The comment is totally right. Technically “to” is the right one.
Comment 34
Line 109, add a space in "24hours". Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Yes, it was fixed in the text.
Comment 35
Line 112, please check there are "were" and "was".
Authors Reply:
“was” is the correct word.
Comment 36
Note, in this manuscript, "twenty-four hours", "24 hours", "ten days" and "10 days" have been used. Please make them in a consistent format throughout the manuscript.
Authors Reply:
The whole manuscript was reviewed, and this comment was fixed.
Comment 37
Line 113, please check the sentence "because all the coatings..." for logical problem.
Authors Reply:
Indeed, this statement is confusion and having problem. The statement does not add any additional or necessary information, thus, we decided to remove this statement from the manuscript.
Comment 38
Line 114, "in" should be deleted.
Authors Reply:
We modified the whole sentence
Comment 39
Line 115, "...at..." should be changed to "...in a..."; and add "...at a given..." before "scan rate".
Authors Reply:
The comment is fixed.
Comment 40
Line 116, "...involve..." should be changed to "...are involved in..."..
Authors Reply:
The comment is fixed.
Comment 41
Line 118, please check the symbol "icorr" should be corrosion current density rather than "corrosion resistance".
Authors Reply:
The comment is totally right.
Comment 42
Line 119 to 120, please check the sentence "...one passes..." that does not make sense.
Authors Reply:
The sentence was deleted.
Comment 43
Line 124, what is "the sample perturbation" here?
Authors Reply:
Line 143 “The measurements were performed at frequencies ranging from high value of 20 kHz to low frequency value of 0.1 kHz to minimize the sample perturbation.”
It means reaching stable frequency and avoiding rapid bouncing of the ions through the coating.
Comment 44
Line 127 to 128, more parameters can be introduced for the XRD analysis.
Authors Reply:
More details were added for XRD analysis.
Comment 45
Figure 1 may be not value added to show the details of the electrochemistry sample holder. Because it not a unique design. Instead, you just need to provide by explaining what the exposure area or diameter is, which is needed in the calculation of the corrosion current density. So, I suggest deleting this figure, if so please remember to reorganize the other figures number in captions and text.
Authors Reply:
We agree with you to delete Figure 1.
Comment 46
Line 149, "...followed by..." should be changed to "...followed with..." in this case. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
It was fixed in the text.
Comment 47
Line 153, the comma "," before "it also..." should be changed to a semicolon ";" in this case.
Authors Reply:
It was fixed in the text.
Comment 48
In the captions of Figure 3, please indicate what types (OM or SEM) of images for (a) to (c)
Authors Reply:
It was added in the text as “Optical”,
Comment 49
Reference [48] has been not shown between [47] and [49]. Please check the make sure all the references are properly numbered and in a order throughout the manuscript.
Authors Reply:
The comment is right. There was a mistake in [48] and [49] references and it was fixed in the text and the Reference section.
Comment 50
Line 167, why use "believed to be"?
Authors Reply:
It is well known phenomenon. Many references prof it such as:
J.A. Gonzalez, M. Morcillo, E. Escudero, V. Lopez, E. Otero, (2005). Atmospheric corrosion of bare and anodized aluminium in a wide range of environmental conditions. Part I: Visual observations and gravimetric results. Surf. Coat. Technol. 153: 225-234.
Krishna, L.R., Purnima, A. S, et al., (2006). A comparative study of tribological behavior of microarc oxidation and hard-anodized coatings. Wear 261(10): 1095-1101, doi.org/10.1016/j.wear.2006.02.002
Comment 51
Line 168, add "is" before "shown".
Authors Reply:
It was fixed in the text.
Comment 52
Line 168, "literature" should be plural in this case.
Authors Reply:
It was fixed in the text.
Comment 53
Line 191, "for" should be changed to "in" in this case.
Authors Reply:
It was fixed in the text.
Comment 54
Line 192, "of" can be changed to "in"; "the" can be deleted before "current density".
Authors Reply:
It was fixed in the text.
Comment 55
Line 198, how did you know the high porosity? you may need to introduce this in Section of "Materials and Methods". "also" can be deleted.
Authors Reply:
The porosity can be seen through the optical images in Fig. 3. High or low was a relative description of the porosity. These was no special technique of measuring the amount of porosity. It is out of the scope of this work.
Comment 56
Line 201, "electrochemistry" can be changed to "electrochemical" in this case.
Authors Reply:
It was fixed in the text.
Comment 57
Line 207, add "the" after "all".
Authors Reply:
It was fixed in the text.
Comment 58
Line 208, what are "materials" here? did you mean "coatings"?
Authors Reply:
Yes, it means coatings and it was fixed in the text.
Comment 59
Line 216, "corrosion" should be changed to "anticorrosion" in this case.
Authors Reply:
It was fixed in the text.
Comment 60
In Figure 6, the horizontal axis and its title do not stay together, one is on the top and the other is on the bottom. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
This has been fixed in Figure 6 and in Figure 7.
Comment 61
In this manuscript some tenses have been not properly used, for example the present perfect tense (have done...). Please check throughout the manuscript for such issues and accordingly adjust all of them to be the right tenses.
Authors Reply:
The whole manuscript was checked and these errors were fixed.
Comment 62
Line 225, delete "the" before "coating thickness".
Authors Reply:
It was fixed in the text.
Comment 63
Line 225 to 228, the discussion and statement about the correlation between coating thickness, coating porosity and electrochemical resistance need references to support your work. One of the good references is as below:
The Roles of Diffusion Factors in Electrochemical Corrosion of TiN and CrN (CrSiCN) Coated Mild Steel and Stainless Steel, (https://doi.org/10.1002/9781118356074.ch7)
Authors Reply:
Thanks for your valuable help. The reference was added in the text as [52] and Reference section.
Comment 64
Line 244 to 245, add "the" after "all".
Authors Reply:
The comment is totally right.
Comment 65
Line 245, suggest adding "systems" after "materials". Since these coatings are kinds of materials systems. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
It was fixed in the text.
Comment 66
Line 259, please check the sentence "by extrapolating ...OCP value." for grammatical problems.
Authors Reply:
This has been modified. You will find it in Line 281.
Comment 67
Line 261, please check if "in" should be "is" or "was"?
Authors Reply:
It was fixed in the text.
Comment 68
Line 275, please check the sentence "...has...were..." for grammatical problems.
Authors Reply:
This has been modified. You will find it in Line 293.
Comment 69
About the current density, different formats of unit have been used. Please check throughout the manuscript and make them all in a consistent format, including those in figures.
Authors Reply:
Yes, it was checked though out the paper.
Comment 70
Line 296 to 297, "phase angle" is mentioned. However, no angle is found in Figures 13 and 14. Please check and make a correction accordingly.
Authors Reply:
The comment is right. Necessary corrections were done.
Comment 71
Line 299, "eye" should be plural in this case.
Authors Reply:
It was fixed in the text.
Comment 72
Line 316, add "the" before "dissolution".
Authors Reply:
It was fixed in the text.
Comment 73
Line 316 to 317, your discussion and statement about coating thickness, porous and electrolyte ion movement, need references to support your work. One of the good references is as below:
The Roles of Diffusion Factors in Electrochemical Corrosion of TiN and CrN (CrSiCN) Coated Mild Steel and Stainless Steel, (https://doi.org/10.1002/9781118356074.ch7)
Authors Reply:
The reference was added in the text as [52] and Reference section.
Comment 74
Line 320, again, please check the reference [48] for it proper order in the manuscript.
Authors Reply:
The comment is right. It was fixed in the text.
Comment 75
Line 347, "fitted" should be changed to for example "combined" ...
Authors Reply:
It was fixed in the text.
Comment 76
Line 351, what "Thin" mean here?
Authors Reply:
It was mistyping mistake. It is “This”.
Comment 77
Line 352, "two time constants" may be written as "two-time constants" so that have a consistent format with "one-time constant".
Authors Reply:
It was fixed in the text.
Comment 78
Line 355, add a semicolon ";" after "obtained" otherwise delete "they".
Authors Reply:
It was fixed in the text.
Comment 80
Line 357 to 358, please check the sentence "...is taking place ...properties..." for grammatical or logical problems, why to the properties?
Authors Reply:
This has been modified.
Comment 81
ine 358 to 360, your discussion and statement need references to support your work. One of the good references is as below:
The Roles of Diffusion Factors in Electrochemical Corrosion of TiN and CrN (CrSiCN) Coated Mild Steel and Stainless Steel, (https://doi.org/10.1002/9781118356074.ch7)
Authors Reply:
It was fixed in the text.
Comment 82
Line 364, please check the use of "uptake" in this case.
Authors Reply:
The sentence has been modified.
Comment 83
Line 374, add "the" before "three types of...".
Authors Reply:
It was fixed in the text.
Comment 84
Line 383, please check the sentence "...is taking place ...properties..." for grammatical or logical problems, why to the properties? also this sentence is copied from that in Line 357, repeating sentences should be avoided.
Authors Reply:
The original statement has been modified and the conclusion statement has been re-written.
Comment 85
Line 384, add "the three" after "All".
Authors Reply:
It was fixed in the text.
Thanks for your guidance and I hope to cooperate with you in the near future.
Best Regards
Sincerely yours,
Essam R. I. Mahmoud (Corresponding author)
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The impedance data in Figures 13 and 19 are not plotted correctly. Nyquist plots should have equal or square axes. That is dimensions of the same magnitude along each axis.
As far as I am concerned this manuscript does not fulfill the standards of Journal Processes.
Author Response
Dear Prof. Editors/ Reviewers:
I thank you very much for your concern about my paper (Ref. No.: processes-386214) and appreciate your valuable comments on my work. Kindly, please find my replying on your comments in the following points:
Reviewer #1:
Comments 1
The impedance data in Figures 13 and 19 are not plotted correctly. Nyquist plots should have equal or square axes. That is dimensions of the same magnitude along each axis.
Authors Reply:
Thanks a lot for your concern and your efforts to improve the accuracy of our work. We totally agree with your comment. Figures 13 and 19 were re-plotted according to your comment. please check the revised manuscript.
Thanks for your guidance and I hope to cooperate with you in the near future.
Best Regards
Sincerely yours,
Essam R. I. Mahmoud (Corresponding author)
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors did all required corrections and modifications. The manuscript can be accepted in its present form.
Author Response
No comments for Reviewer #2 as he accept the paper in its present form.
Reviewer 3 Report
accept in present form
Author Response
No comments for Reviewer #3, as he accept the paper in its present form.
Reviewer 4 Report
The authors have made a very good improvement in this revision. However, there are still some issues, mainly writing and format, need to be resolved.
Line 16, "macrostructure" should be changed to "microstructure". Please check through the manuscript for the same problems and fix them all.
Line 23, "performance" should be plural here. Please check through the manuscript for the same problems and fix them all.
Line 44, "it" can be deleted in this case.
Line 54, add "as" after "such".
Line 87, "structure" should be changed to "microstructure" in this case. Please check through the manuscript for the same problems and fix them all.
Lin 89, "x-ray" should be written as "X-ray". Please check through the manuscript for the same problems and fix them all.
Line 122, the semicolon ";" can be changed to ", i.e.,..." in this case.
Note that in the text "Fig. X" have been used, however, in the captions of figures, "Figure 1" have been used. Please make them in a consistent format throughout the manuscript, to make it easier for the readers to search for them.
Line 153 to 154, please provide the wavelength and scanning rate in XRD.
In Figure 1, what is the exposure area or diameter of the O-ring?
In Figures 13, 14, 19, and 20, units (for example "Ωcm2") must be provided for the accordingly axis.
Line 383, add "it can be seen that..." before "for". add "the" after "all". add "systems" after "material".
Line 391, please check the use of "maneuver" in this case. Did you mean "penetration"?
Line 409, delete "resistance" in this case, since "impedance" and "resistance" are redundant.
In the List of Reference, some new references have been added. However, some of the authors' names are not provided or are not correct. For example, in [53], "et al" should be avoided and all the authors' names should be properly provided in the List of References. In [56], there should be three authors, you only provided two, and the names are not correct, first name and last name have been swapped. Please check all the new added references for these problems and fix them in the revision.
Author Response
Dear Prof. Editors/ Reviewers
I thank you very much for your concern about my paper (Ref. No.: processes-386214) and appreciate your valuable comments on my work. Kindly, please find my replying on your comments in the following points:
Reviewer #4:
Comments 1
The authors have made a very good improvement in this revision. However, there are still some issues, mainly writing and format, need to be resolved.
Authors Reply:
Thanks for your comment
Comments 2
Line 16, "macrostructure" should be changed to "microstructure". Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Fixed in the revised manuscript
Comments 3
Line 23, "performance" should be plural here. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Fixed in the revised manuscript
Comments 4
Line 44, "it" can be deleted in this case.
Authors Reply:
Fixed in the revised manuscript
Comments 5
Line 54, add "as" after "such".
Authors Reply:
Fixed in the revised manuscript (Line 63)
Comments 6
Line 87, "structure" should be changed to "microstructure" in this case. Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Fixed in the revised manuscript
Comments 7
Lin 89, "x-ray" should be written as "X-ray". Please check through the manuscript for the same problems and fix them all.
Authors Reply:
Fixed in the revised manuscript
Comments 8
Line 122, the semicolon ";" can be changed to ", i.e.,..." in this case.
Authors Reply:
Fixed in the revised manuscript (Line 123)
Comments 9
Note that in the text "Fig. X" have been used, however, in the captions of figures, "Figure 1" have been used. Please make them in a consistent format throughout the manuscript, to make it easier for the readers to search for them.
Authors Reply:
This was done according the Journal format
Comments 12
In Figures 13, 14, 19, and 20, units (for example "Ωcm2") must be provided for the accordingly axis.
Authors Reply:
The units of X and Y axis were added in the manuscript for Figures 13, 14, 19 and 20.
Comments 13
Line 383, add "it can be seen that..." before "for". add "the" after "all". add "systems" after "material".
Authors Reply:
Fixed in the revised manuscript
Comments 14
Line 391, please check the use of "maneuver" in this case. Did you mean "penetration"?
Authors Reply:
Maneuver means here “move, drill and take off some of the materials”
Comments 15
Line 409, delete "resistance" in this case, since "impedance" and "resistance" are redundant.
Authors Reply:
Fixed in the revised manuscript
Comments 16
In the List of Reference, some new references have been added. However, some of the authors' names are not provided or are not correct. For example, in [53], "et al" should be avoided and all the authors' names should be properly provided in the List of References. In [56], there should be three authors, you only provided two, and the names are not correct, first name and last name have been swapped. Please check all the new added references for these problems and fix them in the revision.
Authors Reply:
All of the references were checked and fixed in the revised manuscript
Thanks for your guidance and I hope to cooperate with you in the near future.
Best Regards
Sincerely yours,
Essam R. I. Mahmoud (Corresponding author)
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
N/A
